Is the macro "CNTPCT_EL0" a built-in gcc? Because I deleted all the
definitions of CNTPCT_EL0 in the project, it can still be compiled, and the
newly added register "CNTVCT_EL0" can be compiled without any definitions
and declarations. ?
On Thursday, September 7, 2023 at 8:54:59 AM UTC+8 bot crack wrote:
> Hi,
> 1. #define arm_read_sysreg_64(op1, crm, val) \
>
> asm volatile ("mrrc p15, "#op1", %Q0, %R0, "#crm"\n" \
> : "=r" ((u64)(val))) The assembly of this macro should be *"mrrc p15,
> "#op1", %Q0, %R0,"*
>
> 2. But aarch64 does not use the cp15 register, I disassembled
> inmates/lib/arm-common/timing.o(arm_read_sysreg(CNTPCT_EL0, pct64);) and
> the instruction was displayed as *"MRS X0, #3, c14, c0, #1" ,*And the
> instruction "*mrrc p15*" cannot be found in it.
>
>
> On Wednesday, September 6, 2023 at 10:14:30 PM UTC+8 Ralf Ramsauer wrote:
>
>>
>>
>> On 06/09/2023 03:40, bot crack wrote:
>> > Hi
>> >
>> > 1. I want to add some register definitions.
>> > 2. I want to know why #define CNTPCT_EL0 SYSREG_64(0, c14) in arm64
>> > *has only two arguments*, but it can be expanded into assembly "MRS
>> > X0, #3, c14, c0, #1"
>>
>> oh yeah, that's finest macro magic!
>>
>>
>> #define CNTPCT_EL0 SYSREG_64(0, c14)
>>
>> #define SYSREG_64(...) 64, __VA_ARGS__
>>
>> leads to the equivalent:
>>
>> #define CNTPCT_EL0 64, 0, c14
>>
>> Usage of CNTPCT_EL0:
>>
>> arm_read_sysreg(CNTPCT_EL0, pct64);
>>
>> with
>>
>> #define arm_read_sysreg(...) _arm_read_sysreg(__VA_ARGS__)
>>
>> So here, we, in fact, have
>>
>> _arm_read_sysreg(64, 0, c14, pct64)
>>
>> Which is defined as:
>>
>> #define _arm_read_sysreg(size, ...) arm_read_sysreg_ ## size(__VA_ARGS__)
>>
>> So we get
>>
>> arm_read_sysreg_64(0, c14, pct64)
>>
>> which is defined as:
>>
>> #define arm_read_sysreg_64(op1, crm, val) \
>> asm volatile ("mrrc p15, "#op1", %Q0, %R0, "#crm"\n" \
>> : "=r" ((u64)(val)))
>>
>> The rest is done by the assembler.
>>
>>
>>
>> > 3. I didn’t understand the definition in
>> > inmates/lib/arm64/include/asm/sysregs.h because I couldn’t find how
>> > to expand the macro definition SYSREG_64
>>
>> #define SYSREG_64(...) 64, __VA_ARGS__
>>
>> SYSREG_64(1,2,foo) => 64, 1, 2, foo
>>
>> These can be used as arguments in further macros.
>>
>>
>> > 4. For example, I want to add a new CNTVCT_EL0 (op0=0b11, op1=0b011,
>> > CRn=0b1110, CRm=0b0, op2=b010) register. How should I do it?
>>
>> I don't know, but have a look at the Linux kernel to see how others did
>> it in a pretty similar way:
>>
>>
>> https://elixir.bootlin.com/linux/latest/source/arch/arm/include/asm/vdso/cp15.h#L32
>>
>>
>> HTH,
>>
>> Ralf
>>
>
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